Study: Eating a serving of dark, leafy greens daily may slow memory decline

Nov. 22 (UPI) -- People who eat and drink more foods with flavonols -- found in certain fruits and vegetables, including kale, tomatoes, apples and oranges, plus tea and wine -- may have slower memory decline in older age, a study published Tuesday suggests.

The findings appeared in Neurology, the journal of the American Academy of Neurology.

According to Dr. Thomas M. Holland, the study's lead author, taking such simple steps as eating more fruits and vegetables and drinking more tea is an easy way for people to take an active role in maintaining their brain health.

"In our study population, those who consumed the highest level of flavonols, an average of seven servings of dark leafy greens a week or one serving of dark, leafy greens a day, versus the lowest [level], had a 32% decrease in their rate of cognitive decline," he told UPI in an email.

Starting dietary modifications and lifestyle interventions earlier in life would most likely yield the best outcomes, Holland said.

That's because changes in the brain, such as the accumulation of amyloid plaques and hyperphosphorylated tau protein or neurofibrillary tangles in the case of Alzheimer's disease, begin perhaps 10 years to 20 years before the onset of easily detectable clinical signs of it.

However, he stressed that healthy behaviors, especially when it comes to food and drink, are always timely.

"The main point ... is it is never too early, or too late to start making healthy lifestyle changes, especially when it comes to diet," Holland said.

"The research presented here adds to the ever-growing body of evidence that what we eat matters. A diet diverse in fruits and vegetables is critical for both cognitive and physical functioning."

Flavonols are a specific subclass of flavonoids, which are molecules found in many fruits and vegetables, along with tea and wine, that have antioxidant and anti-inflammatory properties and are known to prevent or diminish cellular damage throughout the body, including the brain, said Holland, assistant professor at Rush Institute for Health Aging, Rush College of Medicine & Rush College of Health Sciences in Chicago.

"Flavonols are primarily found in kale, beans, tea, spinach, broccoli, tomatoes, apples, wine, oranges, pears and olive oil. That being said, this is not an exhaustive list," Holland said. "It is just where the largest concentrations of flavonols are found."

The highest level of flavonols generally is contained in the leaf or skin of the vegetable or fruit, and in lower concentrations in the extract or juice, Holland said.

So, although black, white or green tea, and wine -- red more so than white wine -- contain flavonols, it isn't a large concentration.

A person would need to drink three to four cups of tea daily to reach the highest level of flavonols, he said.

He added: "But, to reiterate, it is very important to consume diverse fruits and vegetables. This will provide the best results regarding the quantity and quality of nutrients and bioactives."

The study involved 961 participants, averaging 81 years old, who did not have dementia. They were followed for an average of seven years.

Annually, the participants completed a questionnaire about how often they ate certain foods, and they were placed into one of five groups based on the amount of flavonols they had in their diet.

They also took cognitive and memory tests each year that included recalling lists of words, and remembering numbers and putting them in the correct order.

They were asked about factors such as their level of education, how much time they spent doing physical activities and how much time they spent doing mentally engaging activities, such as reading and playing games.

According to the researchers, the average daily intake of flavonols among U.S. adults is about 16 to 20 milligrams. The study's elderly participants consumed less, averaging roughly 10 milligrams of flavonols per day; the lowest group averaged about 5 mg. per day, and the highest group, 15 mg.

After adjusting for other factors that could affect the rate of memory decline, the investigators found the cognitive scores of people who consumed the highest amount of flavonols declined more slowly than people who had the lowest intake.

Holland said this is probably due to the inherent antioxidant and anti-inflammatory properties of flavonols, but further research is needed.

The study focused on four types of flavonols: kaempferol, found in kale, beans, tea, spinach and broccoli; quercetin, found in tomatoes, kale, apples and tea; myricetin, found in tea, wine, kale, oranges and tomatoes; and isorhamnetin, found in pears, olive oil, wine and tomato sauce.

Dietary intake of kaempferol and quercetin was associated with slower global cognitive decline, but myricetin and isorhamnetin were not, the researchers found.

The scientists noted that the food frequency questionnaire used in the study was self-reported, and people may not accurately remember what they have eaten.

The research was supported by the National Institutes of Health, National Institute on Aging, and Department of Agriculture's Agricultural Research Service.